The present invention concerns a contacting system which seals, without interruption, the stator winding terminal in spindle motors.
Spindle motors are mainly used for driving hard disk drives. Due to the demand for higher and higher storage densities for hard disk drives, endeavours are constantly being made to make their geometrical dimensions increasingly smaller and more compact. Further development of hard disk drives therefore also results in lower and lower flight heights of the read and write heads over the rotating storage medium. At the same time the access times must be reduced to obtain a quicker and higher data throughput, and this in turn requires higher speeds for the hard disk drives. To avoid read and write errors due to head crashes, that is, the read and write heads touching or catching on the hard disk, the requirements of the degree of cleanness for the atmosphere enclosed within the drive are getting higher and higher.
From the need to protect storage media and read/write heads from contamination and mechanical damage, results the demand for a higher and higher degree of cleanness of the air in the drive. This means that both the number and size of permitted particles per unit of volume as a measurable variable for the degree of cleanness are getting smaller and smaller.
The desired lifespan of such storage media is as a rule five years. A necessary prerequisite for meeting this lifespan requirement is that the interior of the drive must be permanently hermetically sealed off from the surrounding atmosphere even at the point of division between motor or shaft flange of the motor and base plate.
Otherwise, due to atmospheric pressure fluctuations there can be an air change and hence uncontrolled pollution or particle contamination of the interior of the hard disks. For this reason, in drives with drop-in motors, that is, motors which are installed in the base plate only after equipment with the disk pack, elastically deformable sealing elements are provided in the joint region between fixed shaft and base plate. In this case the motor shaft which is extended axially downwards and externally threaded is provided with a flange which is collar-like above the base plate. Due to the nut screwed onto the thread from the outside, to the sealing element located between collar and base plate is applied a force under whose influence the sealing element is elastically deformed and in the process compressed in an axial direction.
The electrical connection for driving the motor is here made by a connector which is located in the outwardly opening shaft end of the motor and which consists of a cylindrical insulating body through which pass contact pins arranged with parallel axes. The electrical connection between the contact pins and the terminal wires of the windings is made by a flexible printed circuit board, referred to as a FPC for short below. This FPC extends from the centre of the shaft radially outwards into the stator region. On the FPC are conductor strips which in the central region above the insulating body are soldered to the inner ends of the contact pins.
In the radially outer region, below the windings mounted on the bundle of laminations, the FPC is crescent-shaped or half-ring-shaped. In this region are provided solder pads on which the terminal wires of the windings are soldered. These solder pads in turn are connected by conductor strips on the FPC to the solder pads provided in the central region and designed for connection of the contact pins.
A solution described in this way was disclosed in U.S. Pat. No. 5,661,352.
A drawback of this solution is that the radially outwardly extending FPC crosses the sealing surface provided on the collar. Hence the sealing surface in the crossing region is lowered by the material thickness of the FPC, step-like junctions being formed on both sides of the FPC. xe2x80x9cHermeticxe2x80x9d sealing by the sealing element located between sealing surface and stop face on the base plate is no longer possible owing to the suddenly varying compression rate of the elastic sealing element in the step region, because two radially oriented capillary gaps by which an exchange of atmospheric volume is made possible are formed in this case.
It is therefore the object of the present invention to produce a seal which on the one hand causes hermetic sealing of the interior of the hard disk from the external atmosphere, especially from the interior of the spindle motor, and on the other hand without extra expenditure allows a conductive connection for the terminals of the spindle motor through the seal.
With the present invention, the formation of capillary gaps and the associated drawbacks are eliminated by the fact that the FPC is provided with a self-contained annular region which is preferably arranged roughly concentrically and which by means of a preferably self-adhesive film layer of roughly the same contour is glued onto the supporting surface of the shaft collar. This self-contained annular surface is extended radially inwards, that is, in a direction towards the centre of the annular surface, by at least one tongue-shaped region on which are arranged the conductor strips needed for contacting. These conductor strips are provided with solder pads to which are soldered the contact pins of the centrally arranged connector, which pins pass through the plastic body. From the contour facing away from the centre of the annular region is provided at least one radially outwardly directed, strip-like projection which ends in a half-ring-shaped to ring-shaped, roughly concentrically arranged region which serves to connect the winding wires coming from the motor windings. Here the winding wires are soldered to corresponding solder pads which are electrically connected by conductor strips to the corresponding solder terminals at the centre.
Due to this construction of the FPC according to the invention, in particular due to the roughly annular self-contained region which is glued to the supporting surface of the shaft collar preferably over the whole area, a step-free peripheral sealing surface without sudden changes of level is formed, so that a sealing element installed when the motor is assembled undergoes the same compression at every point all round. Since on the other hand the rear side of the FPC in said region is glued to the supporting surface of the shaft collar over the whole area by the film-like adhesive layer provided according to the invention, hermetically sealing assembly of the motor in the base plate is ensured.
The present invention therefore solves the problem of the exchange of volume at least at the junction between motor and base plate, which is triggered by atmospheric pressure fluctuations and caused by inadequate sealing of the clean-space region of the disk drive, in which are arranged the storage media with the associated read/write heads. Thus later contamination of the clean-space region by particles from the polluted ambient atmosphere in this junction region is prevented.
The annular construction of the FPC in the central area, and gluing of this area over the whole surface on the rear side to the supporting surface formed on the shaft flange, produce a plane, self-contained, step-free sealing surface which allows uniform compression of the elastic sealing element, for example an O-ring, and prevents in particular radially oriented capillary gaps from forming, so that the interior of the hard disk drive is permanently hermetically sealed off from the contaminated environment.
The construction according to the invention and gluing of the annular area of the FPC over the whole surface on the rear side therefore now ensure that pressure fluctuations of the atmosphere do not cause an exchange of volume and therefore can no longer contaminate the clean-space region of the drive even later.